Denture-induced stomatitis is a common clinical condition characterized by oral mucosal lesions, and is prevalent among denture users, particularly elderly or institutionalized patients. Adherence of Candida albicans to denture surfaces is the primary cause of denture-induced stomatitis. Other microbial species reported to contribute to the condition include Streptococcus oralis, Streptococcus sanguis, Porphyromonas gingivalis and Prevotella intermedia. Treatment of denture-induced stomatitis is problematic due to incomplete disinfection of the surface and rapid microbial recolonization of the dental prosthesis.
Typically, “pellicles,” which contain high molecular weight salivary glycoproteins and immunoglobulins, including mucins, amylase and secretory IgA together with natural cationic antimicrobial peptides, form a thin film on surfaces of the oral cavity. On non-prosthetic surfaces, antimicrobial peptides such as histatins, defensins, and bactenecins, derived from saliva, mucosal epithelial cells and neutrophils, are a key protective component of the mucosal and enamel pellicles. Histatins and bactenecins, in particular, have been shown to exhibit antifungal and antibacterial activity against Candida albicans and other oral pathogens. These cationic peptides are adsorbed onto the tooth and oral mucosal surfaces by electrostatic forces.
In contrast, protective antimicrobial peptides are not present in the pellicle which forms on the denture surfaces. Dentures are conventionally made of polymethyl methacrylate (PMMA), which has polar ester groups but no ionically charged groups. The absence of ionic charge on PMMA facilitates the adhesion of Candida albicans and other microbial species onto denture surfaces by preventing the selective adsorption of antimicrobial peptides in saliva to prosthetic surfaces.
Introducing carboxylate groups into PMMA-based denture material to provide carboxylate ions on the surface has been shown to enhance adsorption of histatins and to decrease adherence of Candida albicans to denture surfaces (Edgerton, M., Raj, P. A., and Levine, M. J., J. Biomed. Mat. Res. 29: 1277-1286, 1995; and Raj, P. A., and Venkataraman, G., Dent. Res. 80: 51, 2001). However, it is not known whether other groups such as phosphate groups can be successfully introduced into denture bases to provide negatively charged surfaces, and further, whether anionic phosphate surfaces have the ability to substantially enhance antimicrobial molecule adsorption as well as microbial adherence inhibition, especially under physiological conditions.